Wireless communication devices have become smaller and more powerful in order to meet consumer needs and to improve portability and convenience. Consumers have become dependent upon wireless communication devices such as cellular telephones, personal digital assistants (PDAs), laptop computers, and the like. Consumers have come to expect reliable service, expanded areas of coverage, and increased functionality. Wireless communication devices may be referred to as mobile stations, stations, access terminals, user terminals, terminals, subscriber units, user equipment, etc.
A wireless communication system may simultaneously support communication for multiple wireless communication devices. A wireless communication device may communicate with one or more base stations (which may alternatively be referred to as access points, Node Bs, etc.) via transmissions on the uplink and the downlink. The uplink (or reverse link) refers to the communication link from the wireless communication devices to the base stations, and the downlink (or forward link) refers to the communication link from the base stations to the wireless communication devices.
Wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.
In some cases, such systems may utilize multiple antennae at the transmitting base station and/or a mobile station to provide multiple signal paths. Some type of combining circuit typically combines or selects the signals from the receiver antennas in an effort to achieve an improved quality signal. Examples of such schemes include a maximum ratio combining (MRC) scheme and a beam-forming scheme. While the beam forming scheme typically yields significant improvements in interference-dominated communications channels, the MRC scheme typically yields significant improvements in noise-dominated communications channels.
Unfortunately, conventional combining circuits implement only a single type of combining scheme that may not yield significant improvements in signal quality over both noise-dominated and interference-dominated communications channels.